The present invention relates to a treatment tool for an endoscope, such as a high-frequency snare, forceps or the like, which is used under observation through an endoscope.
Japanese Patent Application KOKAI Publication No. 9-534 discloses such type of treatment tool for an endoscope. In that publication, the treatment tool is formed as a basket type forceps as shown in FIG. 14. The basket-type forceps comprises an operation wire inserted through a sheath 1 and basket wires 3 provided at a distal end portion of the operation wire. The basket wires 3 are moved forwards and backwards by operation through the hand operation section 2, and the basket wires 3 are thereby extended from the distal end portion of the sheath 1 or retracted thereinto. The hand operation portion 2 has an operation body 4 and a slider 5 slidable on the outer circumferential surface of the body. A pair of finger flanges 6 are formed on the slider 5 and a ring 7 is provided at a rear end portion of the operation body 4.
When the basket wire 3 is operated, an operator inserts his or her thumb into the ring 7 and holds and clamps the part of the slider 5 between the pair of flanges 6 with his or her forefinger and middle finger. In this manner, the operation body 4 can be moved forwards and backwards and the operation wire can also be thereby moved forwards and backwards through the sheath 1.
Meanwhile, U.S. Pat. No. 5,496,330 discloses an example of another type of treatment tool for an endoscope. In this type of treatment tool for an endoscope, a proximal end portion comprises a base portion which an operator can grasp on the palm of his or her hand and a slider projected sidewards such that the slider can be operated by the thumb of the same hand. A sheath is connected with the slider. In this manner, the operator can move forwards and backwards the slider by the thumb while holding the base section on the palm.
In case of the treatment tool for an endoscope shown in FIG. 14, a thumb is inserted into the ring 7 of the operation body 4. Therefore, an operator scarcely drops the operation portion after the operator grasps the operation portion. Accordingly, the operator can reliably operate the tool.
However, since this type of treatment tool for an endoscope is operated by only three fingers, several operators cannot have a clear feeling of operating the tool and feel unreliable on it. When the basket wires 3 are extended from or retracted into the distal end of the sheath 1, the operation wire can be moved without moving the sheath 1. Therefore, to grasp a stone at a predetermined position, the basket wire 3 must be contracted while drawing back the basket wire 3 connected to the distal end of the operation wire, into the sheath. Therefore, the basket wire 3 moves in relation to the stone, making it difficult to grasp the stone.
Meanwhile, the endoscope treatment tool described in the U.S. Pat. No. 5,496,330 is operated by the entire of one hand, the operator can easily have a clear feeling of operating the tool. However, there is an operational drawback that it is difficult to apply a handling force to move backwards the slider to tighten the basket wires. In addition, the operator feels a fear that the operation portion may slip on his or her hand and may drop the tool.
Thus, two operation methods have been adopted in a conventional treatment tool for and endoscope, and each of the methods provides both of merits and demerits. Which of the methods is better depends on the operator's choice and cannot be determined definitely. However, it is not economical to prepare both treatment tools adopting different operation methods for the sake of one certain medical operation or for every operator, and management of equipment stocks is complicated. If there occurs a situation that one of the operation methods had better be changed to the other during one medical operation, the conventional treatment tools for an endoscope cannot deal with such a situation because each of the conventional treatment tools is limited to only one of the above-described methods.